1. Field of the Invention
The present invention relates to the field of multi-layered printed circuits or semiconductors and their manufacture, and particularly to the field of large area radiation detectors, their construction and their manufacture.
2. Background of the Invention
Many different types of electronic configurations are formed on one surface or in one layer and electrically connected to other devices or configurations. For example, semiconductor devices such as integrated circuits are integrated into a substrate (such as silicon wafers) in the form of patterned zones in both horizontal and vertical directions. The zones in the horizontal planes may be conductive or semiconductive to provide specific responses to electrical or radiation influences. The zones may also be formed of materials and arrangements which are of different conductivities. This type of construction is important for transistor and diode manufacture. Many thousands of individually responding units can be placed on single wafers by known techniques.
Large area radiation detecting devices have some features which are similar to integrated circuit wafers, but have many different physical and functional requirements. A large area radiation detector must capture radiation in small areas of the detector surface and then be able to capture, convert or release that information in a form readable by other devices. This type of detector is a significant advance over earlier versions of radiation capture devices in which radiation was captured by phosphors, then emitted upon stimulation by applied radiation (these types of devices shown for example in U.S. Pat. No. Re. 31,847 and U.S. Pat. Nos. 4,258,264; 4,315,318; 4,387,428; and 4,276,473). Devices in which the radiation was released as different wavelengths of light were easily configured to generate images (hard copy or electronically captured a second time), but there was a significant reduction in resolution because of the nature of the image conversion and recapture.
Large area radiation detectors provide an opportunity for direct electronic conversion of impacting radiation into electronic signals. It is a part of this process to collect charge (electronic signals) which is a representation of image information or data. The limitation on resolution in the image electronically transmitted from the detector is the resolution of the electronic structure and scanning process. With the many advances made in circuit construction, the resolution of circuitry can excede the resolution readily perceived by unaided visual examination.
In the formation of integrated circuits, where the dimensions between layers is very small (e.g., less than 5 micrometers), conductive interconnectors can be formed between layers by etching thin layers (on top of one electronically active layer) to leave small conductive posts on which is built another electronically active layer (with or without an insulative material filling in the area between the posts). U.S. Pat. No. 5,244,534 describes such a process for forming posts between layers in an integrated circuit. The constraints on the insulating composition (if any) between layers is not significant because the dimensions are so small. Significant percentages of shrinkage, for example, are not highly detrimental, since no filling composition is essential as there is little physical structural support needed in the wafers.
Large area detectors are much larger devices than integrated circuitry and also requires greater thickness to withstand higher levels of physical stress and reduce capacitive signal coupling due to the large number of electrode crossovers common to many circuit paths. Where integrated circuit layer separations are generally on the order of 5 microns or less, large area detectors must be greater than 50 micrometers in thickness, and often may be from 75-200 micrometers in thickness. It can be readily seen that with a full order of magnitude difference in thickness, different physical needs must be met in the different constructions between integrated circuitry and large area detectors. Integrated circuit die periphery dimensions (its sides) are also generally on the order of one-half inch (1.27 cm) or less, while large area detectors are presently used with up to seventeen inches (43.2 cm) per side.